GaAs同质外延生长过程的RHEED分析

Reflection High Energy Electron Diffraction Studies of GaAs Homoepitaxial Growth Process

采用激光分子束外延方法(L-MBE),在GaAs(001)衬底上同质外延GaAs薄膜。利用反射式高能电子衍射(RHEED)研究了材料沉积过程中的各级条纹及其强度的变化,进而得出GaAs薄膜外延生长的适宜激光能量和沉积温度分别为500 mJ和570℃。RHEED强度随时间的变化曲线表明,GaAs为良好的层状外延生长模式,并随着沉积时间延长,层状生长模式逐渐向岛状模式转变。实验研究还表明层状生长的GaAs薄膜经表面弛豫后,可以得到更好的平整表面,并出现GaAs(001)-(2×4)的表面重构。原位X射线光电子能谱仪(XPS)研究表明沿(001)面外延的GaAs薄膜表面Ga∶As化学计量比约为52∶48,出现Ga的聚集。

The homoepitaxial GaAs thin film was deposited on GaAs （001） substrate by using laser molecular beam epitaxy （L-MBE）. With in situ monitoring of RHEED, the diffraction intensity with the various patterns was investigated during the deposition. It was demonstrated that the proper laser energy and deposition temperature for homoepitaxial GaAs thin film were 500 mJ and 570℃ respectively. In combination with RHEED intensity oscillation curves, the layer-by-layer growth mode was obtained. With the increasing of deposition time, the transformation from layer-by-layer growth mode to islands growth mode was observed. Besides, the smoother surface and the surface reconstruction of GaAs （001） - （2 × 4） were obtained through the surface relaxation. In situ X-ray photoelectron spectroscopy （XPS） investigation shows that the concentration of Ga is greater than As on the surface, and Ga：As ratio is about 52：48 during the deposition process.